Graphene is simply one atomic layer of graphite - a layer of sp2 bonded carbon atoms arranged in a hexagonal or honeycomb lattice. Graphite is a commonly found mineral and is composed of many layers of graphene. The structural make-up of both graphene and graphite, and their fabrication methods are slightly different. This article highlights the difference between these two materials.
Graphite is one of the three naturally occurring allotropes of carbon and occurs naturally in metamorphic rock in different parts of the globe, including South America, Asia and some parts of North America. This mineral is formed as a result of the reduction of sedimentary carbon compounds during metamorphism.
The chemical bonds in graphite are similar in strength to those found in diamond. However, the lattice structure of the carbon atoms contributes to the difference in hardness of these two compounds; graphite contains two dimensional lattice bonds, while diamond contains three dimensional lattice bonds. The carbon atoms within each layer of graphite contain weaker intermolecular bonds. This allows the layers to slide across each other, making graphite a soft and malleable material.
Various studies have demonstrated that graphite is an excellent mineral with several unique properties. It conducts heat and electricity and retains the highest natural strength and stiffness even in temperatures exceeding 3600°C. This material is self-lubricating and is also resistant to chemicals.
Although there are different forms of carbon, graphite is highly stable under standard conditions. Depending upon its form, graphite is utilized for a wide range of applications.
Graphene: Wonder Material
Graphene has unique properties that exceed those of graphite. Although graphite is often used to reinforce steel, it cannot be utilized as a structural material on its own because of its sheer planes. In contrast, graphene is the strongest material ever found; it is more than 40 times stronger than diamond and more than 300 times stronger than A36 structural steel.
Since graphite has a planar structure, its electronic, acoustic, and thermal properties are highly anisotropic. This means, phonons pass much more easily along the planes than they do when trying to pass via the planes. However, graphene has very high electron mobility and, like graphite, is a good electrical conductor, due to the occurrence of a free pi (p) electron for each carbon atom.
However, graphene has much higher electrical conductivity than graphite, due to the occurrence of quasiparticles, which are electrons that function as if they have no mass and can travel long distances without scattering. In order to fully realize this high level of electrical conductivity, doping needs to be carried out to overcome the zero density of states which can be visualized at the Dirac points of graphene.
Creation or Isolation of Graphene
Scientists use a number of techniques to produce graphene. Mechanical exfoliation, also known as the adhesive tape technique, is one effective way of creating single layer and few layer graphene. However, various research institutions worldwide are trying to find the most efficient way of creating high-quality graphene cost effectively on a large scale.
Chemical vapour deposition (CVD) is the most suitable technique for producing monolayer or few layer graphene. This technique is capable of extracting carbon atoms from a carbon rich source by reduction. However, a major drawback in this technique is the difficulty in locating a suitable substrate to grow graphene layers on as well as the complexity in removing the graphene layers from the substrate without altering or damaging the graphene’s atomic structure.
Other techniques for growing graphene are sonication, thermo-engineering, carbon dioxide reduction, cutting open carbon nanotubes, and graphite oxide reduction. This latter technique of using heat to reduce graphite oxide to graphene has recently attracted significant attention owing to reduced cost of production. Nonetheless, the quality of graphene produced presently does not meet the theoretical potential of the material and will take some more time to perfect.
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